The specific aims of this study are to study the total innervation of the pulp of a single rat molar tooth. The study involves an elucidation of (1) numbers and types of nerve fibers passing through the apical foramina of the tooth, (2) how many cell bodies account for these fibers, and (3) the location of the cell bodies. For location of cell bodies, the study will include an analysis of the trigeminal, superior cervical sympathetic, otic, and cervical dorsal root ganglia and the mesencephalic nuclei of the fifth cranial nerve. Methods include the retrograde transport of horseradish peroxidase (HRP) from the tooth pulp, locating and counting HRP positive cell bodies light microcopically, making total nerve fiber counts at the apical foramina of molars from unoperated control animals and from animals in which a superior cervical sympathetic ganglion was extirpated. The analysis of nerve fiber numbers and types will be done electron microscopically. The results of these studies will serve as the basis for the understanding of the function of pulpal innervation.